Low and slow is not going to make the difference. It is a matter of not stopping the cook until the meat is done. In the case of pork butt, you can go until the bone wiggles loose easily or until it probes like butter. This will normally be somewhere in excess of 200-205 degrees internally.
Custom Offset/GMG Davy Crockett/Vision Kamado/Blackstone/WSM 14.5" X2/Jumbo Joe/KCBS